Beat-frequency oscillator



Filed March 2, 1962 I I I I I I I I I I I I Q I 1M E5: I \l m.\ I I I I I I I I I I .I I I I1 I I I I I I I I I I I Il" n Q Q I M EXE A mm\T/ mmk. I I I I I I I I I l I I I I l I I I I I I I I I I I 2| I1 Li. mm1 -.m\, n I I I I I I I I I I I I I lL Etam M .om N m I I 52.358 A 5&5@ I .x m 11.15.

INVENTOR RICHARD D. CRAWFORD BY 9. My-.-

ATTORNEY United States Patent O 3,168,711 BEAT-FREQUENCY OSCILLATOR Richard David Crawford, Palo Alto, Calif., assigner to Hewlett-Packard Company, Palo Alto, Calif., a corpo- 2 ration of California Filed Mar. 2, 1962, Ser. No. 176,964 4 Claims. (Cl. 331-39) This invention relates to a multi-range beat-frequency oscillator.

There are many systems in the prior art which show the generation of a iixed frequency from a crystal-controlled oscillator or other accurate source, the multiplication or division of this fixed frequency to obtain a number of harmonically-related fixed frequencies, the selection by means of a range switch of a selected one of these fixed frequencies and its mixing with the output of a variablefrequency oscillator to obtain continuous output-frequency coverage.

lt is the principal object of this invention to provide a multi-range beat-frequency oscillator of outstanding simplicity.

It is a further object of this invention to provide a multi-range beat-frequency oscillator in which dividerstages for different ranges operate at frequencies which are so similar that the divider stages can be identical in design.

The drawing shows a block diagram of a beat-frequency oscillator in accordance with this invention.

The beat-frequency oscillator in accordance with this invention is designed to provide output frequencies Af in a plurality of ranges Af, A/n, Af/n2, .Af/n3 and Af/n'i' Where n is an integer greater than one. In the specic example shown in the drawing7 n=10 and the ranges are therefore decades. It comprises a crystal oscillator 11 operating at the frequency (niUF, a buffer amplifier 13 and a (nil) frequency divider 15 the output of which is the frequency F. The purpose of this arrangement is to have two signal sources, one for the frequency (niUF and one for the frequency F. This purpose could also be accomplished by having an oscillator operating at the frequency F and a (ni l) frequency multiplier the output of which would be the frequency (nDF. The frequency division system, however, is preferred over one employing frequency multiplication in order to reduce random incidental phase modulation at the frequency (niDF. The output F of divider 15 is fed to an input terminal of mixer 17. It also comprises a third signal source, namely a variable-frequency oscillator 19 operating at the frequency F. I:Af. The output frequency F :L-Af of oscillator 19 is variable to permit the variation of the output frequency Af.

The output frequency F- tAf of oscillator 19 is fed through a buffer ampliler 21 and contact 23 of range switch 25 to another input terminal of mixer 17. The output frequency of mixer 17, with the range switch at position :23, is therefore FFiAf=Af.

The output frequency FiAf of oscillator 19 is also fed to an input terminal of mixer 27, while the output frequency (ni-DF of oscillator 11 is fed .to the other input terminal of mixer 27. The output frequency of mixer 27 is [(n t1)Fi (Fi-.AHL it is fed to frequency divider 29 which divides it by the factor n to yield F-ev This

3,168,7ll Patented Feb. 2, 1965 ICE #teen-ea The output frequency eea of divider 29 is fed to a input terminal of mixer 33, while the output frequency (niUF of oscillator 11 is fed to the other input terminal of mixer 33. The output frequency of mixer 33 is it is fed to frequency divider 35 which divides it by the factor n to yield eea frequency is fed through contact 37 of range switch 25 to an input terminal of mixer 17. Since a signal of frequency F is fed to the other input terminal of mixer 17, its output with the range switch at position 37 is Fraai-e Similarly, the output frequency of divider 35 is fed to an input terminal of mixer 39, While the output frequency (ni l )F of oscillator 11 is fed -to the other input terminal of mixer 39. The output frequency of mixer 39 is is fed to a frequency divider 41 which divides it by the factor n to yield la@ ns This This

Fif n3 frequency is fed through contact 43 of range switch 25 to an input terminal of mixer 17. Since F is fed to the other input terminal of mixer 17, its output with the range switch at position 43 is The beat-frequency oscillator can be provided with several more stages to provide Af Af F etc. In each instance the mixer of a given stage is fed with the output of oscillator 11 and with the output of the n-divider of the preceding stage. The output of that mixer is divided by n and fed to a contact of range switch 25.

The principal advantage of the beat-frequency oscillator of this invention is that the mixer-divider combina- 'tions 27-29, 33-35, 39-41, etc. operate at frequencies i interchangeable modules.

60-5 kilocyclfes pen second 6,000-500 cycles per second 60G-50 cycles per second 60-5 cycles per second 10 6-5 cycle per second f .t-.05 cycle per second .06---005 cycle per second rl`he frequency, (rz- 1)F, of crystal oscillator 1l is 5 15 rnegacycles.Y Since the ranges are in decades (11:10), the output of divider l5 divides the 5 megacycles by 9 so that Y the frequency F is 555.555- kilocycles.V The variable frequency oscillator i9 operates from 495.555--7- to 550.5557--4- kilocy'cles. With the output of oscillator iii set at 550.55544- kilocycles, the signals applied to the input terminals of mixer 27 are 5 megacycles and 55t).555- kilocycles; the signals applied` to the input terminals of mixer 33 are-5 megacycles and 555.055--- kilocycles; the signals applied to the input terminals offmixer 39 are 5 megacycles and 555.505--Y kilocycles. As this process is repeated inthree more stages, the 5 magacycle signal remains the samerand the other signals applied to the mixers become, in succession, 555;5505-- kilocycles, 555.55505' kilocycles, and 555.555505- kilocycles. Thus it will be apparent that the mixers and dividers of the six stages can be made of identical and Successively more stages can be added in order to extend the frequency range downward as far as desired.V n 35 I claim: l

l. A beat-frequency oscillator designed to produce output frequencies of Af, Af/n, if/n? and rif/n3, where n is an integer greater than one, and'comprising:

a rst signal source operating at the frequency (niUF,

a second signal/'source connected to said first signal t source and designed to produce the frequency F,

. a third signal source operating at the frequency FiAf,

output mixing means Vto mix the output F of said second signal source with vthe outputFiAf of said third signal source to obtain the frequency Af, f mixing'means tomix the output. (n- I-UF of said rst signal source with the output YFini of said third signal source to. obtain l the frequency [(ni1)Fi(FiAf)l,

a first frequency divider connected to said lastnamed mixing means and designed to divide the {(nil)Fi(Fi-Af)] frequency by n to obtain the frequency l output mixing means to mix the output F of said second signal source with theoutput i Fi i n Y of said first frequency divider to obtainrthe frequency Af/n, f mixing means to mix the output (r1- PUF 'of said first signal source With the output i Af, FinY of said first frequency divider to obtain the frequency Y te-uninet a second frequency divider connected to said last-named mixing means and designed to'divide the [(1st Qrlilri ,n frequency by n to obtainthe frequency and output mixing means toy mixl the output F of second signal source with the output Fif-f n2 Y of said second frequency divider to obtain A f '1t-2 2. A beat-frequency oscillator designed to produce out-V put frequencies ofl A/n, lf/n2 and idf/113, Where nis an integer greater than one, andicomprising:

a first signal source operating at the frequency (nillF,

a second signal source connected toV said first signal,V

source and designed to produce the frequency F,

' a third signal source operating at the frequency F idf,

mixing means to mix the output (niDF of said first signal source With the output FiAf of said third signal source to obtain the Vfrequency [(uiDFFi-Afu, Y Y

a first frequency divider connected to said lastnamed mixing means and designed to dividevthe [(nil)Fi(FiAf-)} frequently by n to obtain the frequency Y t Y mixing means to mix the output (niUF of said first signal sourceV with the output Fit-f of said firstV frequency divider to obtain the frequency [oeuil-tee] 'a second frequency dividerconnected to said. lastnamed mixing means andVV `designed to divide the [(niQr-jril] 'il'V frequency by n to obtain the frequency 3. in a beat-frequency oscillator designed to producer` output frequencies in a plurality of ranges defined by successive powers of 11,' u being an integer greater than one:

meansfto produce first and second frequencies, saidiirst frequency 'being exactly (nj- 1) times greater than-said secondpfrequenc means to produce a third frequency, a

plurality of stages each comprising a mixer and an ndivider connected to the output of said mixer, means to apply the output of said lirst'frequency source to an input terminal of each of said mixers, means to apply the output of said third frequency source .to the other input terminal of the mixer of the lirstof said stages,'means to apply to the input terminal of the mixer of a succeeding stage the output frequency of the divider of thev preceding stage,

an output mixer, and means including a range vswitch to apply to said output mixer said second frequency and said' another frequency selected from said third frequency and Vthe output of one of the dividers from said stages.

4. In a beat-frequency oscillator designed :to produce output frequencies in a plurality of ranges dened by successive powers of n, n being an integer greater than one: means to produce first and second frequencies,

said first frequency being exactly (nil) times greaterv than said second frequency, means to produce a third frequency, a plurality of stages each comprising a mixer and an n-divider connected to the output of said mixer, means to apply the output of said rst frequency source to an input terminal of each of said mixers, means to apply the output of said third frequency source to the other input terminal of the mixer of the first of said stages,

6 means to apply to the input :terminal of the mixer of a succeeding stage the output frequency of the divider of the preceding stage, an output mixer, and means including a range switch to apply to said output mixer said second frequency and another frequency selected from the output of one of thedividers from said stages.

References Cited by the Examiner UNITED STATES PATENTS 2,574,326 11/51 Goldstine 331--38 2,957,144 10/60 Huhn 331--51X ROY LAKE, Primary Examiner.

JOHN KOMINSKI, Examiner. 

4. IN A BEAT-FREQUENCY OSCILLATOR DESIGNED TO PRODUCE OUTPUT FREQUENCIES IN A PLURALITY OF RANGES DEFINED BY SUCCESSIVE POWERS OF N, N BEING AN INTEGER GREATER THAN ONE: MEANS TO PRODUCE FIRST AND SECOND FREQUENCIES, SAID FIRST FREQUENCY, BEING EXACTLY (N+1) TIMES GREATER THAN SAID SECOND FREQUENCY, MEANS TO PRODUCE A THIRD FREQUENCY, A PLURALITY OF STAGES EACH COMPRISING A MIXER AND AN N-DIVIDER CONNECTED TO THE OUTPUT OF SAID MIXER, MEANS TO APPLY THE OUTPUT OF SAID FIRST FREQUENCY SOURCE TO AN INPUT TERMINAL OF EACH OF SAID MIXERS, MEANS TO APPLY THE OUTPUT OF SAID THIRD FREQUENCY SOURCE TO THE OTHER INPUT TERMINAL OF THE MIXER OF THE FIRST AND SAID STAGES, MEANS TO APPLY TO THE INPUT TERMINAL OF THE MIXER OF A SUCCEEDING STAGE THE OUTPUT FREQUENCY OF THE DIVIDER OF THE PRECEDING STAGE, AN OUTPUT MIXER, AND MEANS INCLUDING A RANGE SWITCH TO APPLY TO SAID OUTPUT MIXER SAID SECOND FREQUENCY AND ANOTHER FREQUENCY SELECTED FROM THE OUTPUT OF ONE OF THE DIVIDERS FROM SAID STAGES. 